How can I place the rollers of a corner roller conveyor evenly?
Doing it by hand can be very precise and actually one of the faster ways.

First figure out how many rollers you need, then divide 90 by that number and you have the amount of degrees between each roller. For this example, I use 9 additional rollers, making it an even 10 degrees.

Then place the 3D-Cursor in the center of your curve and set the pivot point in the header to 3D-cursor.



Select your roller, duplicate it with SHIFTD and then without even confirming that hit R10RETURN.

That way, Blender considers duplication and rotation as a single action, not two.

You can now use the repeat hotkey SHIFTR to create lots of rollers and they will be rotated evenly around the cursor. No manual translation needed anymore.

If they don't have to turn, you could use an array modifier with object origin or dupliframes, spin tool or similar, but this solution is the fastest that I know and leaves the rollers as separate objects, ready for animation.

Sometimes it might be useful to put the object center of the rollers into the center of the curve using set origin in the tools area. But you should be fine with the method mentioned above.

You can use ALTD to create linked copies instead of SHIFTD if you want to save a bit of memory and filesize. All rollers will then use the same mesh.